The arctic tundra is home to the lemming, a small, stocky rodent famous for two largely misunderstood behaviors: supposed aggression and mass suicide. Lemmings are not much larger than a typical mouse, yet their reputation far exceeds their size. This perception is built on a mixture of observation, misinterpretation, and fabrication, which has obscured the actual reality of their complex survival strategies. The truth about lemming behavior, particularly their temperament and dispersal movements, is far more nuanced than popular folklore suggests.
Temperament and Typical Social Behavior
Under normal conditions, lemmings are largely solitary creatures that maintain individual territories, living quietly in burrows beneath the snow or tundra vegetation. They focus their energy on foraging for grasses, mosses, and sedges. This baseline behavior is typical of many small rodents whose primary defense is to remain hidden from predators like foxes, owls, and weasels.
However, certain species, particularly the Norwegian lemming (Lemmus lemmus), exhibit an unusual defensive strategy when directly confronted. Instead of retreating, they may turn to face a potential threat, adopting an aggressive posture, hissing, and emitting loud, high-pitched squeaks. This behavior is considered a form of aposematism—a warning display—signaling to predators that they are not worth the trouble. This defense is a specialized adaptation to the open tundra where cover is scarce, allowing the rodent a split second to startle and escape a predator.
Behavior During Population Peaks
The reputation for widespread aggression is largely linked to the lemming’s population cycles, which typically peak every three to five years. During these peak years, densities can become extremely high, reaching up to 1,000 individuals per hectare in some areas. This intense overcrowding quickly exhausts local food resources and triggers stress responses.
The resulting lack of food and high social density drastically alters their behavior, driving disorganized movements in search of new territory. These movements are desperate, resource-seeking dispersals often misinterpreted by observers as a collective state of rage. Increased physical interactions, such as pushing and shoving among individuals competing for limited space and food, also contribute to the perception of generalized aggression. Scientific studies suggest that these density-dependent changes may be linked to hormonal shifts. This high-stress environment causes individuals to become highly visible and vocal, cementing their aggressive reputation as they move across the landscape.
Debunking the Myth of Mass Suicides
The most enduring misconception about lemmings is the myth that they deliberately commit mass suicide by plunging off cliffs into the sea when their population becomes too large. This inaccuracy was popularized by the 1958 Disney film White Wilderness, which was later revealed to have staged the footage by herding lemmings off a precipice. The true nature of their movements involves accidental drownings during their dispersal phases.
As lemmings move across the landscape searching for a new habitat, they will attempt to cross any obstacle, including wide rivers and lakes. Lemmings are capable swimmers, but they are not prepared for the vastness of large bodies of water or the exhaustion of an extended swim. When large groups reach the shore of a wide river or fjord, many will enter the water simultaneously. Those that fail to find the other side or become waterlogged in the cold water will drown. The sight of numerous drowned rodents washing up on the shore is a consequence of disorganized movement and misjudgment, not a suicidal pact driven by a desire to control population numbers.